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Knowledge Base: The Effects of Myostatin in Red Polls

1

Apr

2013

In the Autumn 2012 Newsletter, an overview was given of the
findings of Dr. Pam Wiener and others at the Roslin Institute in Edinburgh as
to the effects of the Myostatin variant in South Devons and it was reported
that we were hoping to secure funding to allow the Society to work with Dr.
Wiener on a study of the effects of the Myostatin variant in Red Polls.

Our application to the Technology Strategy Board for £5,000
was successful and, as a result, an additional 300 samples were tested for the
variant by Neogen ( although 20 of these were unacceptable and produced no
result.) 60% of the 370 animals tested were non –carriers, as shown in the
table.

All

Males

Females

M0

221

60%

56

55%

165

61%

M1

137

37%

42

42%

95

35%

M2

12

3%

3

3%

9

4%

Totals

370

101

269

289 of the animals tested had Signet Records and Dr. Wiener
went on to assess the effect of the Myostatin variant on Birth weight, Calving
Ease, Fat Depth, Muscle Depth and adjusted 100 to 500 day growth. We wanted to
see what the effects were and whether they were or were not similar to the
effects found previously in the S. Devons and
other Native Breeds. We did not have any data to assess the effect on carcase
weight or carcase quality.

Fat Depth and Muscle Depth

As with other Breeds, it was found that the Fat Depth
decreased with the number of copies of the variant such that the M2 had about
1.5mm less fat than the M1 and the M1 had about 0.5mm less fat than the M0, the
difference between the M2 and the M0 therefore being about 2mm.

Conversely, Muscle Depth increased with the number of copies
of the variant such that the M2 had about 3.5 mm more muscle depth than the M1
and the M1 had about 3.5mm more muscle depth than the M0, the difference
between the M2 and the M0 therefore being about 7mm.

Birth Weight and Calving Ease.

The average Birth Weight in Red Polls was 40.81 Kgs. The
variant had no statistically significant effect on birth weight [although the
M2 animals, of which there were 10, were heaviest at birth and at 100 days.]

On Signet, Calving Ease is measured on a score of 1 – 5
where 1 represents no assistance and 5 represents a Caesarean. Overall, the Red
Polls had a score of 1.1, meaning there were very few which needed any
assistance. There was no evidence that the variant had any effect, adverse or
beneficial, on calving ease. The 10 M2 animals all had a score of 1 (no
assistance.) There was no evidence that the M1 was heavier at birth or had any
decreased calving ease

Growth Rate.

At ages over 100 days the M1 was heavier than either the M2
or the M0 although this was not a statistically significant difference. There
was insufficient data to assess the effects on 500 day growth but at 300 days
the effect was statistically significant: the M1 animals were 13 Kgs. heavier
at 300 days than either the M0 or M2 animals

Comparison with South Devons.

The frequency of the variant is similar in the Red Polls and
the S. Devons.

From the previous article it can be seen that, unlike in the
Red Polls, the number of copies of the variant had a significant adverse effect
in the S. Devons on Birth Weight (the S. Devon M0 averaged 40 Kg, the M1
averaged 41.3 Kg and the M2 averaged 44.9 Kg) and on Calving Ease (the S. Devon
M0 scored 1.4, itself worse than the average Red Poll, the M1 scored 1.6 and
the M2 scored considerably higher at 2.2, i.e. probably all the M2s needed at
least some assistance in calving.) There was also a significant difference
between the Red Polls and the S. Devons in the effect of the variant on Growth
Rate. In the S. Devons, the M0 and the M1 had similar growth rates but the M2
was some 31 Kg. lighter than the M0 at 252 days (36 weeks.) In the Red polls on
the other hand, it was the M0 and M2 which had similar growth rates and the M1
was 13 Kg. heavier at 300 days (43 weeks.)

Interpretation.

When considering the implications of this study it is
important to bear in mind that there are obvious limitations because of the
relatively small sample size [289 animals for the main analysis whereas the
2009 report on S. Devons had 835 for the calving score, 995 for the birth
weight and 2,300 for growth rate.] Nevertheless, it is suggested that this has
proved to be a very interesting and worthwhile study providing a number of
statistically significant results in various areas. It had always been thought
that, although the same Myostatin variant [nt821] was present in different Breeds,
the effects of that variant might well differ to a greater or lesser extent
between different Breeds. That has been proved to be the case here with very significant
differences between the effects on Birth Weight, Calving Ease and Growth Rate
in the S. Devons and the Red Polls.

In essence, this study shows that, in the Red Polls at least,
the variant acts beneficially to reduce Fat Depth and to increase Muscle Depth
but without the adverse effects seen in other Breeds on Birth Weight and Calving
Ease, there being no evidence that the variant increases Birth Weight or
Calving difficulty in Red Polls. There is the added benefit that the M1 has a
higher growth rate than the M0 and the M2 such that the M1 animals were 13 Kg.
heavier than the M0 or M2 animals at 300 days. With stores making over £2.00
per Kg. this would give a very worthwhile additional £26.00 per head.

Acknowledgements.

The Society is very grateful for the funding received from
the Technology Strategy Board and for the participation and assistance given by
Dr.PamWiener of Roslin Institute, Gary Evans of Neogen, Sam Boon of Signet, and
all those who provided hair samples from their animals.

If anyone would like a copy of the Report or further
information or clarification, please email simon_temple@hotmail.co.uk